The ordeal only ended when police were dispatched to the scene, with Sidney and Andrew finally confirmed who they were.
The duo, both of Cross Place Dudley, were punished for their offending at Telford Magistrates' Court on April 25.
The court heard how Sidney and Andrew were at Poole Hall Fishery, Alverley, Shropshire, on September 6, 2023.
They were fishing when they were approached by two bailiffs who were checking fishing licences, the Environment Agency said. Andrew refused to give officers his details and told his dad not to as well.
According to the Environment Agency, failing to provide your details when requested by a water bailiff is an offence.
The officers cautioned Andrew for not providing his details but he became verbally and physically abusive. He threatened the officers and started moving his equipment. The officers 'feared for their safety' and moved a fishing knife away from the convicts. When the bailiffs said they were removing fishing gear for evidence, Andrew hit one officer in the face. Sidney then tried to grab the officer's chest, where his radio was, and 'poked him in the eye with flailing arms'.
The court heard how Andrew had to be taken to the ground after he refused to allow the officers to handcuff him.
Andrew continued to give officers incorrect details, claiming he was called David Wilkes and lied about where he lived. Police were called, with Andrew and Sidney finally providing their correct details.
Sidney admitted two counts of assaulting an emergency worker and one count of fishing without a licence. He was ordered to pay an £806 fine, a £322 victim surcharge and £4,000 costs.
Andrew admitted two counts of assaulting an emergency worker, two counts of obstructing a water bailiff and one count of fishing without a licence. He was handed a £634 fine, a £253 victim surcharge, £50 compensation and £6,000 costs.
Environment Agency water bailiffs are considered constables 'for the purposes of enforcing fisheries legislation' and are protected under the Assaults on Emergency Workers (Offences) Act 2018.
A spokesperson for the Environment Agency said: "These sentences handed out show that the courts will not allow assault of public servants to go unpunished.
"It sends out a strong message to other people trying to stop our officers from performing their duties. "Our officers do endure abuse and threats of violence in carrying out important work to protect people and the environment. "The Environment Agency will not hesitate to prosecute those that obstruct or assault its staff.
"If people suspect illegal fishing incidents they should call our 24/7 hotline on 0800 807060."